Just like sleeping bags, jacket warmth is mainly a function of loft, all other things being equal. 3" of 600 fill down/feathers will keep you warmer than 2" of 800 fill. Of course the 600 fill will be heavier per cubic inch but winter insulation when it's -20 is not a good place to be counting ounces.

Fit, as mentioned above, and construction also come into play. Both jackets appear to have sewn-through construction and are probably about equal in that regard. I would also consider how well the neck/cuffs/hem seal in the heat.

What is the loft of these jackets? Unlike sleeping bags it's rarely in the specs. You'll probably have to do a direct comparison using more than just an image on a computer monitor. Maybe you can find a B&M store that sells both, or order both online and then return one.

You're making a big investment in an important piece of gear. It may be worth your while to invest time and effort in making the right choice.